§1.1 Field of the Invention
The present invention concerns methods, apparatus and data structures for providing a transport network that supports a virtual LAN service. More specifically, the present invention concerns emulating a transparent LAN segment to support a virtual LAN. The present invention also concerns configuring such a network.
§1.2 Related Art
The description of art in this section is not, and should not be interpreted to be, an admission that such art is prior art to the present invention.
§1.2.1 Known Private Networking Technologies
For many entities (such as businesses, universities, etc.), local area networks (LANs) suffice for intra-entity communications. Indeed, LANs are quite popular since they are relatively inexpensive to deploy, operate, and manage, and are based on mature, well-developed technology, such as Ethernet, for example. Unfortunately, however, most entities need to communicate (voice and/or data) with their own facilities, or others, beyond their immediate location. Thus, wide area networks (WANs) are needed. Very often, entities want at least some privacy or security attached to their communications.
Presently, private long-haul communications can take place over networks that can be generally classified into two types—dedicated WANs that facilitate communications among multiple sites, and public transport networks that allow one or more sites of a private network to communicate. Both of these types of networks are introduced below.
Dedicated WANs are typically implemented using leased lines or dedicated circuits to connect multiple sites. Customer premise equipment (CPE) routers or switches at these sites connect these leased lines or dedicated circuits together to facilitate connectivity between each site of the network. Unfortunately, dedicated WANs are relatively expensive and typically require the customer to have some networking expertise.
Public transport networks, which are typically deployed by regional bell operating companies (RBOCs), or some other service provider, are often used to allow remote users to connect to an enterprise network using the public-switched telephone network (PSTN), an integrated services digital network (ISDN), or some other type of transport network technology. (Note that the word “public” in the phrase “public transport network” denotes the fact that more than one entity may use it, even though it may be privately owned and managed, and not available to the general public.) Such remote access may be facilitated by deploying network access servers (NASs) at one or more central cites. When users connect to (e.g., dial into) a NAS, it works with authentication, authorization and accounting (AAA) servers to verify the identity of the user and to check which services that user is authorized to use.
Transparent LAN services (TLS) would be an attractive service to many customers of Service Providers. One instance where such an offering could be provided is in a metropolitan area, where one or more multi-tenant buildings are connected to a central office, and several central offices are connected with one other via a transport network. Often, a Service Provider will deploy a simple, low-cost device (dubbed a multi-tenant unit (MTU)) in each building. Each of the MTUs has at least one link with a service provider edge unit (L3PE) in one or more offices. Thus, although customers are not connected to a single LAN, since they may be spread across a metro area or a wide area, the transparent LAN service will appear to such customers as a single LAN.
As can be appreciated, private dedicated WANs are beyond the financial reach of many entities. Accordingly, so-called public transport networks have become quite popular. However, providing transparent LAN segment services via MTUs, which typically have on the order of 10 to 100 Ethernet ports and one or more uplinks to an edge device (L3PE), poses challenges with regard to scalability, as well as performing configuration, discovery and learning functions in a simple, cost-effective way.
Thus, an alternative public transport network is needed. Such a public transport network should (i) support the provision of virtual private network functions, (ii) be easy for a service provider to deploy (provision and configure) and manage, (iii) allow customers to use a mature technology that is easy to install, use and manage, such as Ethernet for example, while shielding them from the complexities of the transport network, (iv) be scalable, and/or (v) provide the needed functionality in a cost effective manner.